This invention relates generally to the production of lightweight, fire resistant roofing shingles or tiles, and more particularly concerns the use of Portland cement in admixtures capable of extrusion to form such roofing pieces.
There is continuous need for improvements in processes to consistently produce strong, lightweight cementitious building products such as tiles, shingles, bricks, blocks, etc., and employing lightweight aggregates together with Portland Cement. In the past, such lightweight building products were difficult to produce, and suffered from undesirably low strengths.
Prior roofing tiles and methods of production are disclosed, for example, in Jakel U.S. Pat. No. 3,841,885, Jakel U.S. Pat. No. 3,870,777, Kirkhuff U.S. Pat. No. 3,852,934 and Murdock U.S. Pat. No. 4,288,959, and Wood U.S. Pat. No. 4,673,659 describing problems encountered in lightweight extruded tile production.